1. Field of the Invention
This invention relates to a two-dimensional scanning apparatus and a scanning type image displaying apparatus using the same, and particularly is adapted to two-dimensionally scan a beam (deflected beam) deflected by deflecting means to thereby project and display a two-dimensional image on a surface to be scanned (a screen surface).
2. Related Background Art
There have heretofore been various two-dimensional scanning apparatuses adapted to two-dimensionally deflect a beam emitted from light source means by deflecting means, and two-dimensionally optically scan a surface to be scanned with a spot to thereby form a two-dimensional image (see, for example, Japanese Patent Application Laid-Open No. H08-146320).
In Japanese Patent Application Laid-Open No. H08-146320, a beam emitted from light source means is deflected by deflecting means capable of two-dimensional deflection, and a surface to be scanned is two-dimensionally scanned with the beam by a scanning lens of which the distortion characteristic has an f·sinθ characteristic. In this publication, the distortion of an image is corrected by the f·sinθ characteristic of the scanning lens and electrical correction.
In Japanese Patent Application Laid-Open No. H11-84291, there is disclosed a two-dimensional scanning optical system using an optical element including a refracting surface and a reflecting surface, and turning back an optical path in the interior of the optical element, and in order to correct eccentric aberration, the refracting surface or the reflecting surface is constituted by a non-rotation symmetrical surface having an axis of rotational symmetry in neither the inside nor the outside of the surface. In this publication, although adopting a two-dimensional scanning optical system constituted by an optical element, the speed constancy of scanning beam on a surface to be scanned is corrected well over a wide scanning angle. It is also made possible to achieve telecentricity necessary for highly accurate image depiction.
As previously described, the two-dimensional scanning apparatus deflects a beam emitted from light source means by deflecting means capable of two-dimensional deflection, and forms a two-dimensional image on a surface to be scanned through a two-dimensional scanning optical system. It is generally known that at this time, image distortion occurs to the two-dimensional scanning image on the surface to be scanned. This is the so-called distortion.
The distortion includes distortion as the distortion of a two-dimensional scanning optical system, the distortion of a constant speed scanning property, TV distortion which indicates that the frame of an image depicted on a surface to be scanned curves, and the like. Also, when an image is obliquely projected onto the surface to be scanned, trapezoid distortion occurs.
In Japanese Patent Application Laid-Open No. H08-146320, TV distortion is corrected by the f·sinθ characteristic of the scanning optical system and electrical correction, however there has been the problem that it is difficult to electrically correct it.
In Japanese Patent Application Laid-Open No. H11-84291, it is also made possible to have a wide scanning angle, correct distortion of a constant speed scanning property and achieve telecentricity, however TV distortion caused by two-dimensional scanning cannot be corrected. In the publication, there has been the problem that when image distortion such as TV distortion and trapezoid distortion occurs, the quality of the image is deteriorated, so that an image of high quality cannot be displayed.